Most women will experience menstrual clots at some point in their lives. Menstrual clots are gel-like blobs of coagulated blood, tissue, and blood that’re expelled from the uterus during menstruation. They resemble stewed strawberries or the clumps of fruit you may sometimes find in jam, and vary in color from bright to dark red.

If the clots are small — no larger than a quarter — and only occasional, they’re usually nothing to worry about. Unlike clots formed in your veins, menstrual clots by themselves aren’t dangerous.

Regularly passing large clots during your period could signal a medical condition that needs investigation.

Normal clots:

  • are smaller than a quarter
  • only occur occasionally, usually toward the beginning of your menstrual cycle
  • appear bright or dark red in color

Abnormal clots are larger than a quarter in size and occur more frequently.

See your doctor if you have heavy menstrual bleeding or you have clots larger than a quarter. Menstrual bleeding is considered heavy if you change your tampon or menstrual pad every two hours or less, for several hours.

You should also seek immediate medical help if you’re passing clots and think you could be pregnant. That could be a sign of miscarriage.

Most women of childbearing age will shed their uterine lining about every 28 to 35 days. The uterine lining is also called the endometrium.

The endometrium grows and thickens throughout the month in response to estrogen, a female hormone. Its purpose is to help support a fertilized egg. If pregnancy doesn’t occur, other hormonal events signal the lining to shed. This is called menstruation, also known as a menstrual period or period.

When the lining is shed, it mixes with:

  • blood
  • blood byproducts
  • mucus
  • tissue

This mixture is then expelled from the uterus through the cervix and out the vagina. The cervix is the opening of the uterus.

As the uterine lining sheds, it pools in the bottom of the uterus, waiting for the cervix to contract and expel its contents. To aid in the breakdown of this thickened blood and tissue, the body releases anticoagulants to thin the material and allow it to pass more freely. However, when the blood flow outpaces the body’s ability to produce anticoagulants, menstrual clots are released.

This blood clot formation is most common during heavy blood flow days. For many women with normal flows, heavy flow days usually occur in the beginning of a period and are short-lived. Your flow is considered normal if menstrual bleeding lasts 4 to 5 days and produces 2 to 3 tablespoons of blood or less.

For women with heavier flows, excessive bleeding and clot formation can be prolonged. One-third of women have flows so heavy they soak through a pad or tampon every hour for several hours.

Physical and hormonal factors can impact your menstrual cycle and create a heavy flow. Heavy flows increase your chances of developing menstrual clots.

Uterine obstructions

Conditions that enlarge or engorge the uterus can put extra pressure on the uterine wall. That can increase menstrual bleeding and clots.

Obstructions can also interfere with the uterus’s ability to contract. When the uterus isn’t properly contracting, blood can pool and coagulate inside the well of the uterine cavity, and form into clots that are later expelled.

Uterine obstructions can be caused by:

Fibroids

Fibroids are typically noncancerous, muscular tumors that grow in the uterine wall. Besides heavy menstrual bleeding, they can also produce:

Up to 80 percent of women will develop fibroids by the time they’re 50. The cause is unknown, but genetics and the female hormones estrogen and progesterone likely play a role in their development.

Endometriosis

Endometriosis is a condition in which the uterine lining grows outside the uterus and into the reproductive tract. Around the time of your menstrual period, it can produce:

The exact cause for endometriosis isn’t known, although heredity, hormones, and previous pelvic surgery are thought to play a role.

Adenomyosis

Adenomyosis occurs when the uterine lining, for unknown reasons, grows into the uterine wall. That causes the uterus to enlarge and thicken.

In addition to prolonged, heavy bleeding, this common condition can cause the uterus to grow two to three times its normal size.

Cancer

Although rare, cancerous tumors of the uterus and cervix can lead to heavy menstrual bleeding.

Hormonal imbalance

In order to grow and thicken properly, the uterine lining relies on a balance of estrogen and progesterone. If there’s too much or too little of one or the other, you could have heavy menstrual bleeding.

Some things that can cause a hormonal imbalance are:

The main symptom of a hormonal imbalance is irregular menstruation. For example, your periods may be later or longer than usual or you may miss them entirely.

Miscarriage

According to the March of Dimes, as many as half of all pregnancies end in miscarriage. Many of these pregnancy losses occur before a woman even knows she’s pregnant.

When an early pregnancy is lost, it can lead to heavy bleeding, cramping, and clotting.

Von Willebrand disease

A heavy menstrual flow could also be caused by von Willebrand disease (VWD). While VWD is rare, between 5 and 24 percent of women with chronic heavy menstrual bleeding are affected by it.

VWD might be the cause of your heavy menstrual cycle if it occurs regularly and you bleed easily after a minor cut or your gums bleed too easily. See your doctor if you suspect this is the cause of your heavy bleeding. They should be able to help get you a diagnosis.

See your doctor if you regularly have large clots. One of the major complications of heavy menstrual bleeding is iron deficiency anemia. Anemia is a condition that occurs when there’s not enough iron in your blood to make healthy red blood cells. Symptoms include:

To determine the underlying cause of your menstrual clots, your doctor will likely ask you about things that impact menstruation. For example, they may ask if you’ve had previous pelvic surgeries, use birth control, or have ever been pregnant. They’ll also examine your uterus.

Additionally, your doctor may use blood tests to look for hormonal imbalances. Imaging tests, such as an MRI or ultrasound, can be used to check for fibroids, endometriosis, or other obstructions.

Controlling heavy menstrual bleeding is the best way to control menstrual clots.

Hormonal contraceptives and other medications

Hormonal contraceptives can inhibit the growth of the uterine lining. A progestin-releasing intrauterine device (IUD) may reduce menstrual blood flow by 90 percent, and birth control pills may reduce it by 50 percent.

Hormonal contraceptives also can be beneficial in slowing the growth of fibroids and other uterine adhesions.

For women who can’t or don’t want to use hormones, a common option is the medication tranexamic acid (Cyklokapron, Lysteda), which affects blood clotting.

Surgery

Sometimes you may need surgery.

A dilation and curettage (D and C) procedure sometimes follows a miscarriage or childbirth. But it can also be used to determine the underlying cause for heavy menstrual bleeding or as a treatment for various conditions.

D and C involves widening the cervix and scraping the uterine lining. It’s usually done in an outpatient setting under sedation. While this won’t cure heavy bleeding, it should give you a respite for a few months as the lining thickens again.

For women with uterine growths like fibroids that don’t respond well to medication, surgery to remove the growths may be necessary. The type of surgery will depend on the size and location of the growths.

If the growth is large, you may need a myomectomy, which involves making a large incision in your abdomen to access the uterus.

If the growth is small, laparoscopic surgery is often possible. Laparoscopy also uses incisions in the abdomen, but they’re smaller and may improve your recovery time.

Some women may opt to have their uterus removed. This is called a hysterectomy.

Talk to your doctor about the pros and cons of all of your treatment options.

Heavy menstrual periods can affect your daily life. Besides the physical problems they can cause, such as cramping and fatigue, they can also make normal activities, such as being physically active, swimming, or even watching a movie, more challenging.

These tips may help you manage your symptoms:

  • Take over-the-counter nonsteroidal anti-inflammatories (NSAIDs) such as ibuprofen (Advil, Motrin) at the start of your period through your heaviest flow days. Besides easing cramping, NSAIDs may help reduce blood loss by 20 to 50 percent. Note: If you have von Willebrand disease, you should avoid NSAIDs.
  • Wear a tampon and a pad on your heaviest flow days. You can also wear two pads together. High-absorbency tampons and pads may also help catch the blood flow and clots.
  • Use a waterproof pad or even a towel placed on top of your sheets at night.
  • Wear dark-colored clothing to conceal any leaks or accidents.
  • Always carry period supplies with you. Keep a stash in your purse, car, or office desk drawer.
  • Know where public bathrooms are. Knowing where the nearest restroom is can help you quickly reach a toilet if you’re passing a lot of large clots.
  • Eat a healthy diet and stay hydrated. Heavy bleeding can take a toll on your physical health. Drink plenty of water and eat a balanced diet that includes iron-rich foods, such as quinoa, tofu, meat, and dark green, leafy vegetables.

Menstrual clots are a normal part of a woman’s reproductive life. While they may look alarming, small clots are normal and common. Even clots bigger than a quarter aren’t noteworthy unless they happen regularly.

If you regularly pass large clots, there are many effective treatments your doctor may recommend to help control heavy bleeding and reduce the clots.